Diesel and glyphosate price changes benefit the economics of conservation tillage versus traditional tillage

Abstract

Recent increases in diesel price and decreases in glyphosate [ N-(phosphonomethyl) glycine] price should favor the profitability and farmer acceptance of herbicide-intensive conservation tillage systems versus fuel-intensive traditional tillage (TT) systems. Profitability results from a long-term field experiment that compared TT, minimum tillage (MT), and delayed minimum tillage (DMT) systems for winter wheat–( Triticum aestivum L.)summer fallow in eastern Washington, USA were calculated using both 1998 and 2005 input prices. Net returns for the MT and DMT systems increased by US$ 6.37 and 6.30 (rotational ha) −1, respectively, and net returns to the TT system decreased by US$ 2.36 (rotational ha) −1 when 2005 versus 1998 prices were used. Here, rotational ha equals 0.5 ha fallow and 0.5 ha wheat. Focusing on the dominant crop of soft white winter wheat (SWWW), the 2005 price hikes pushed diesel costs up for all systems, from US$ 6.81 (rotational ha) −1 for DMT to US$ 9.00 (rotational ha) −1 for TT. The cost of diesel for the conservation tillage systems, relative to the cost for TT, decreased by US$ 1.50–2.20 (rotational ha) −1. The conservation tillage systems accrue greater savings from the price reduction in glyphosate because they consume more of this herbicide. An unanticipated result was that relative cost savings from price changes in N fertilizer rivaled those from diesel and glyphosate because anhydrous NH 3–N was exclusively used in the experiment for TT and aqueous NH 3–N for MT and DMT. The price of anhydrous NH 3–N increased from US$ 0.55 kg −1 in 1998 to 0.85 kg −1 in 2005, a 56% increase. Aqueous NH 3–N only increased from $0.75 kg −1 in 1998 to 0.85 kg −1 in 2005, a 15% increase. The greater price increase for anhydrous NH 3–N penalized the TT system because of its use of this fertilizer. If the same source of N fertilizer were used on all three tillage systems, this fertilizer cost effect would disappear. Nonetheless, the conservation tillage systems still retained a statistically significant profitability advantage over TT even if the same fertilizer was used throughout. The sharp price increase for diesel and the concurrent price decrease for glyphosate herbicide favored the conservation tillage systems over TT in this study. Results provide strong evidence for the superior profitability of conservation tillage winter wheat–summer fallow under current economic conditions.